1. Field of the Invention
The present invention relates to a portable gas detector, and particularly to a portable gas detector equipped with a gas sucking means for introducing a gas to be detected into it and capable of detecting plural kinds of gas components.
2. Description of the Background Art
There are generally frequent occasions when it may be possible in, for example, underground job sites or gateways, or other places where persons enter, or working regions that air in an environmental atmosphere is in a dangerous state, or will become a dangerous state, such as occasions when hazardous gases such as carbon monoxide and hydrogen sulfide gases may possibly be contained in air in such an environment, or when the oxygen gas concentration in air may possibly be lowered.
When the air in the environmental atmosphere has become a dangerous state to persons due to high concentration of the dangerous gases contained or low oxygen gas concentration, it is necessary to immediately sense the fact.
From such a demand, there have heretofore been proposed various types of portable gas detectors. Some of these portable gas detectors are provided with a plurality of gas sensors respectively detecting gas components different from each other in such a manner that the plurality of the gas components can be detected at the same time (see, for example, Japanese Patent Application Laid-Open No. 2002-116169).
When for example, carbon monoxide gas is detected by such a gas detector capable of detecting a plurality of gas components as described above, a gas sensor composed of a controlled potential electrolysis type gas sensor element is generally used. In order to conduct the intended gas detection without being affected by an interfering gas, for example, hydrogen sulfide gas or the like, it is conducted to provide a filter for removal of interfering gases having a function of removing the interfering gas component related to the gas sensor in an gas intake of the gas sensor.
In such a portable gas detector, however, a method, in which a gas to be detected that is, for example, air in an object space to conduct gas detection, is introduced into a gas sensor by natural diffusion, is utilized. It may be however necessary in some cases to introduce the gas to be detected into the gas sensors by forcedly sucking the gas to be detected by a gas sucking means such as a pump.
In a portable gas detector having a plurality of built-in gas sensors, however, it generally becomes large in size and heavy in weight when the gas sucking means is provided in the body of the gas detector and hence involves problems that it is considerably unhandy to carry and is a great obstacle to practice the intended work or the like.
In addition, exchange of the filter for removal of the interfering gases often requires a complicated operation, for example, disassembly of the gas detector.